God's Permission

If people only will go to heaven with god's permission, so why we must struggle to do all the obligations ?

Answer :

I give you a simple analogy

When you study in a college or university
There is a lot of students there
And you are not such a brilliant student
You're just and ordinary student, need to be more hardworking
When teacher or your lecturer marking your paper,
 he knows who really are you
maybe your answer not brilliant enough, but still, 
he knows that you have tried all your best
At least, he marks your paper not very strict
And then you can pass the exam :)

" We do not enter the paradise because of our deeds, but because of His mercy"(hadeeth)

Allah knows better